Musannaf Ibn Abi Shayba 13:1902

Abu Bakr narrated to us, he said: Muhammad ibn Bishr narrated to us, from Ali ibn Salih, from Mughirah, from Ibrahim, he said: The right of wala’ (patronage) belongs to the one who emancipated [the slave], whether the slave strove [to pay for his freedom] or did not strive.